This invention pertains to bidentate square planar heteroleptic complexes of (pyridyl)azolate ligands, and particularly to their use in organic light emitting diodes (“OLEDs”), semi-conducting materials, and other applications.
Luminescent organic or metal-organic molecular materials have a range of applications. These include organic light emitting diodes (“OLEDs”) that exhibit white or monochrome electroluminescence. Such devices may be utilized in solid-state lighting (“SSL”), which accounts for 22% of total electrical power consumption in the U.S., and also for video display in electronic devices such as TV, camcorders, monitors, cell phones, etc. In particular, utilization of phosphorescent metal-organic complexes in OLEDs has allowed higher device performance than that allowed by fluorescent organic materials because the phosphorescent metal-organic complexes allow radiative recombination of both triplet and singlet excitons (with an upper limit of 100% efficiency compared to 25% for fluorescent organic materials).
Traditional OLED fabrication methods require doping in order to achieve high efficiencies. This is problematic for multiple reasons: Precise control over the doping concentration is difficult and can lead to inhomogeneity in thin films thus affecting performance and color rendering. Second, incomplete host-guest charge transfer and charge leakage results in decreased efficiency that become especially burdensome at higher voltages. It is therefore desirable to eliminate the need for doping in an OLED device while maintaining high performance.
Another area of intense interest is in organic thin film transistors “OTFTs”. These devices, along with other organic electronics, rely on p-type and/or n-type semiconducting materials to function properly. Although p-type semiconducting organic materials have been realized with high hole mobilities, n-type semiconductors which conduct electrons have not been able to maintain the same performance.